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Enterococcus faecium resistant to ampicillin and gentamicin

D T Tsukayama1, B Wicklund, R P Gruniger

  • 1Musculoskeletal Sepsis Unit, Hennepin County Medical Center, Minneapolis, Minnesota, USA.

International Journal of Antimicrobial Agents
|September 1, 1992
PubMed

Insights

Ampicillin-resistant Enterococcus faecium strains were identified, showing resistance to multiple antibiotics including beta-lactams. These findings highlight a critical need for novel therapeutic strategies against multidrug-resistant enterococcal infections.

Area of Science:

  • Medical Microbiology
  • Infectious Diseases
  • Antimicrobial Resistance

Background:

  • Ampicillin-resistant enterococci, particularly Enterococcus faecium, pose a significant challenge in healthcare settings.
  • The emergence of multidrug-resistant strains necessitates understanding their resistance mechanisms and clinical implications.

Purpose of the Study:

  • To characterize ampicillin-resistant Enterococcus faecium isolates from clinical specimens.
  • To assess their susceptibility patterns to various antibiotics and combinations.
  • To investigate potential genetic determinants of resistance.

Main Methods:

  • Isolation and identification of enterococcal strains from clinical specimens.
  • Determination of minimum inhibitory concentrations (MICs) for ampicillin, penicillin, imipenem, ampicillin-sulbactam, amoxicillin-clavulanic acid, and gentamicin.
  • Evaluation of synergistic bactericidal activity of gentamicin with penicillin or vancomycin.
  • Detection of beta-lactamase activity using nitrocephin test.
  • Plasmid DNA analysis to identify common resistance markers.

Main Results:

  • Thirty ampicillin-resistant enterococci were isolated, identified as Enterococcus faecium.
  • All isolates exhibited high MICs for ampicillin and penicillin, and resistance to imipenem, ampicillin-sulbactam, and amoxicillin-clavulanic acid.
  • Susceptibility to vancomycin was observed in all isolates.
  • Limited gentamicin resistance (10%) was noted, but no synergistic bactericidal effect was demonstrated with gentamicin combinations.
  • No beta-lactamase activity was detected.
  • Plasmid analysis revealed a common band in 29 of 30 resistant isolates, absent in sensitive strains and Enterococcus faecalis.

Conclusions:

  • The study identified multidrug-resistant Enterococcus faecium strains with resistance to multiple beta-lactams and lack of gentamicin synergy.
  • A common plasmid band may be associated with ampicillin resistance in these isolates.
  • The limited treatment options underscore the urgent need for new strategies to combat enterococcal infections.

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